wnl CLI / win-nightlight-lib

A Rust library and CLI for manipulating the Windows 11 night light settings.

NOTE: Tested on Windows 11 24H2 (OS Build 26100.3476). This may not be guaranteed to work on older Windows versions.

win-nightlight-lib

The win-nightlight-lib library includes basic functionality to parse and modify the Windows night light settings from the user's registry. The night light state and settings are stored in a binary format located at:

• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\CloudStore\Store\DefaultAccount\Current\default$windows.data.bluelightreduction.bluelightreductionstate\windows.data.bluelightreduction.bluelightreductionstate
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\CloudStore\Store\DefaultAccount\Current\default$windows.data.bluelightreduction.settings\windows.data.bluelightreduction.settings

As the format is in binary, the implementation for serialization & deserialization is done at a best-effort basis based on resources found online for reverse-engineered format interpretations. See the documentation for NightlightSettings and NightlightState for more details regarding the data structure interpretations. Currently, the only unknown part about the data structures is related to the latter bytes of the NightlightState - any contribution towards this would be greatly appreciated!

wnl.exe CLI Usage

Usage: wnl.exe <COMMAND>

Commands:
  temp      Sets the color temperature in Kelvin (1200 - 6500)
  schedule  Sets the schedule mode ('off', 'solar', or 'manual')
  on        Enables nightlight
  off       Disables nightlight
  status    Prints the current nightlight state and settings
  help      Print this message or the help of the given subcommand(s)

Options:
  -h, --help     Print help
  -V, --version  Print version